A Systematic Comparison of Designs to Study Human Fecundity.

Background: Several epidemiologic designs allow studying fecundability, the monthly probability of pregnancy occurrence in noncontracepting couples in the general population. These designs may, to varying extents, suffer from attenuation bias and other biases. We aimed to compare the main designs: incident and prevalent cohorts, pregnancy-based, and current duration approaches.

Realizing a desired family size: when should couples start?

Study Question: Until what age can couples wait to start a family without compromising their chances of realizing the desired number of children?

Summary Answer: The latest female age at which a couple should start trying to become pregnant strongly depends on the importance attached to achieving a desired family size and on whether or not IVF is an acceptable option in case no natural pregnancy occurs.

What Is Known Already: It is well established that the treatment-independent and treatment-dependent chances of pregnancy decline with female age. However, research on the effect of age has focused on the chance of a first pregnancy and not on realizing more than one child.

Too old to have children? Lessons from natural fertility populations.

Study Question: Is it possible to construct an age curve denoting the ages above which women are biologically too old to reproduce?

Summary Answer: We constructed a curve based on the distribution of female age at last birth in natural fertility populations reflecting the ages above which women have become biologically too old to have children.

What Is Known Already: The median age at last birth (ALB) for females is ∼40-41 years of age across a range of natural fertility populations. This suggests that there is a fairly universal pattern of age-related fertility decline.

The effect of postponement of first motherhood on permanent involuntary childlessness and total fertility rate in six European countries since the 1970s.

Background: Postponement of childbearing since the 1970s has led to an increase in permanent involuntarily childlessness. We will address the magnitude of this trend, the effect of IVF/ICSI and the effect on total fertility rate (TFR an often used demographic measure for the level of fertility) in six EU countries.

Methods: Using a fertility micro-simulation model, we estimate the effect of postponement of first motherhood on permanent involuntary childlessness in six representative European countries since 1970/1985: Sweden, Austria, Czech Republic, The Netherlands, West Germany and Spain.

A Pilot Study of the ELFE Longitudinal Cohort: Feasibility and Preliminary Evaluation of Biological Collection.

Etude Longitudinale Française depuis l'Enfance (ELFE) will be a national French cohort of 20,000 children followed from birth to adulthood. Biological samples will be taken at birth to evaluate the fetal exposition to several substances. A pilot study was carried out in October 2007 to test the preanalytical factors that affected sample quality.

Bisphenol-A and phthalates contamination of urine samples by catheters in the Elfe pilot study: implications for large-scale biomonitoring studies.

Exposure to phthalates and Bisphenol A could cause developmental and reproductive toxicity. This study provides a first assessment of these exposures for more than 250 French pregnant women. The median concentrations of total and free Bisphenol A in urine were similar to those in other studies except the highest concentrations (5% of women had total and free Bisphenol A >50μg/L).

Changes in sexual behaviours: from secular trends to public health policies.

Objective: To explore the relative contribution of secular trends and public health policies to changes in sexual behaviour.

Design: Three random probability surveys of the sexual behaviour of people aged 18-69 years were conducted in 1970, 1992 and 2006 in France.

Methods: Data of the 2006 survey (n = 12,364) were compared with those from two surveys carried out in 1970 (n = 2625) and 1992 (n = 20,055).

Rationales, design and recruitment for the Elfe longitudinal study.

Background: Many factors act simultaneously in childhood to influence health status, life chances and well being, including pre-birth influences, the environmental pollutants of early life, health status but also the social influences of family and school. A cohort study is needed to disentangle these influences and explore attribution.

Methods: Elfe will be a nationally representative cohort of 20 000 children followed from birth to adulthood using a multidisciplinary approach.

The effect of in vitro fertilization on birth rates in western countries.

Background: We will assess to what extent in vitro fertilization (IVF) is effective in increasing the number of births overall and whether earlier application of IVF will increase this number.

Methods: We simulate 100 000 women trying for their first and second child. Natural and IVF pregnancy rates and infertility rates are age-dependent and based on published data.

A new estimate of permanent sterility by age: sterility defined as the inability to conceive.

The proportion of couples permanently sterile beyond a certain age is an important component of the reproductive process. Unless medical assistance is used, this age is the upper bound of the fecund period. Most estimates of sterility by age of the woman have been derived from natural fertility populations, in which the number of births and the timing of the last birth (of the complete reproductive history) were not controlled by the couples.

Studies of fertility and fecundity: comparative approaches from demography and epidemiology.

The approaches used by demographers and by epidemiologists for studying the fecundity of couples (i.e. their ability to conceive) have converged, whereas they were historically divergent.

Contraception at the time of abortion: high-risk time or high-risk women?

Background: Despite the widespread use of highly effective contraception in France, the incidence of abortion is high. A retrospective population-based cohort study was designed to analyse women's contraceptive history.

Method: We compared the contraceptive use of 163 women, whose last pregnancy ended in abortion, 6 months before, at the time of, 1 month and 6 months after the event with that of 1787 women who had never had an abortion.

Demographic effects of the introduction of steroid contraception in developed countries.

The use of the contraceptive pill increased very rapidly in the 1970s in many developed countries, and fertility almost simultaneously started to decline. We discuss here the possibility of a causal link between these two major changes. We first provide evidence for a relationship between the spread of oral contraceptive use and the change in fertility in many European countries over the last three or four decades.

Feasibility of the current-duration approach to studying human fecundity.

Approaches for monitoring time trends in couples' fecundity and for studying its sensitivity to environmental factors are needed. Two approaches rely on the inclusion of a cross-sectional sample of couples currently "at risk" of pregnancy either with follow up (prevalent cohort) or without follow up (current-duration design). To illustrate the feasibility of the current-duration design, we contacted a random sample of 1204 French women age 18 to 44 years in 2004 and recruited those who were currently having unprotected sexual intercourse.

Towards less confusing terminology in reproductive medicine: a proposal.

The use of the term 'infertility' and related terms in reproductive medicine is reviewed. Current terminology is found to be ambiguous, confusing, and misleading. We recommend that the fertility investigation report of a couple should consist of statements concerning description, diagnosis, and prognosis.

Can assisted reproduction technology compensate for the natural decline in fertility with age? A model assessment.

Background: Maternal age is an important factor in reproduction. Can assisted reproduction technologies (ART) fully compensate for the decline in fertility with age?

Methods: We used a computer simulation (Monte Carlo) model of reproduction, combining the monthly probabilities of conceiving, the risk of miscarriage and the probability of becoming age-dependently permanently sterile.

Results: Under natural conditions, 75% of women starting to try to conceive at age 30 years will have a conception ending in a live birth within 1 year, 66% at age 35 years and 44% at age 40 years.

Contraception: from accessibility to efficiency.

Background: Despite the widespread use of medical contraception in France, the prevalence of abortion remains stable. A cross-sectional population-based survey was designed to study the characteristics of current contraceptive use in France, the different types of contraceptive failure, and the reasons reported for not using contraception.

Methods: A representative sample of 14 704 French households was randomly selected from the telephone directory.

[The many states of aging: a meeting and some demographic aspects].

With an expectation of life at birth of 27 years in the middle of the 18th century, 21% of males reached their 60th birthday with a remaining expectation of life of 12 years. Under the conditions of mortality of 1950, in France, 70 percent could celebrate their 60th birthday, and they had still 15 years (only) to live on the average. This last figure started increasing after 1950: the expectancy of life at age 60 is now over 20 years, and it will exceed 25 years around 2050 (for women, the mean will be 31 years).